... a lot of people respond to this by saying the criticisms are stupid, that "if you know what you're doing" then you'll understand what's really going on, etc.
Yes; "if you're just willing to get your hands a little dirty and muck in and learn then you can bend the hugely complicated interface to your needs" they'll say; they'll complain that your just not willing to learn things, and thus it is your fault. Such people will inevitably state that they are "power users" who need ultimate configurability and are (unlike you) willing to learn what they need to to get that.
For those of us who learned to "customize our desktop" back in the days of FVWM via scriptable config files calling perl scripts etc. it seems clear that "power users" are really just posers who want to play at being "super-customised". Almost all the modern DEs do have complete customisation available and accessible; some of them just use a richer (scripting) interface to get such things done.